Stricture formation is a common complication of Crohn's disease resulting in severe morbidity, intestinal obstruction and surgical intervention. The overall objective of this proposal is to determine the pathologic mechanism of this stricturing process with the ultimate goal of providing modalities for therapeutic intervention. On the basis of our preliminary work, we propose the hypothesis that these strictures result from increases in collagen and muscle in the bowel wall and that the accumulating collagen is synthesized by smooth muscle cells in response to chronic inflammation. We will test this hypothesis by: 1) comparing the collagen content and smooth muscle thickness in surgically resected normal, inflammed and strictured human intestine. Collagen will be quantitated by determination of hydroxyproline; the thickness of the different smooth muscle layers will be quantitated morphometrically in histologic sections of the same specimens; 2) comparing the types of collagen in normal, inflammed and strictured bowel. Collagen types I, III and V will be quantitated biochemically; immunohistochemical studies will determine to locus of types I, III, IV and V in the same specimens. These studies will determine whether collagen accumulates in strictures due to a change in the relative proportions of the different types in the bowel wall. An increase in the proportion of type V would suggest that smooth muscle cells are synthesizing the collagen in strictures; 3) examining the effects of inflammatory cells and inflammatory mediators on the proliferation and collagen synthesis of human intestinal smooth muscle cells in vitro. Human intestinal smooth muscle cells will be isolated from normal human bowel. Inflammatory cells will be isolated from peripheral human blood, and from the lamina propria of normal and inflammed human intestine. These studies will determine if, in the formation of strictures, the chronic inflammatory infiltrate characteristic of Crohn's disease stimulates smooth muscle cells to proliferate and synthesize more and/or different types of collagen. Current technology available to the collagen biochemist has not at yet been applied to the fibrosis complicating Crohn's disease. This proposal will provide information that will contribute significantly to an understanding of the mechanism of stricture formation in this devastating disease and, hence, form the basis for future therapies to be used for its control and amelioration.